Glass and other ceramic fibers are commonly manufactured by supplying molten ceramic to a bushing, drawing fibers from the bushing, applying a chemical treatment, such as an aqueous-based system, so as to size the drawn fibers, and then gathering the sized fibers into a tow or strand.
In order to fabricate composite parts, the fibers are often further chemically treated in an off-line impregnation process with a polymeric resin. The resin has been a thermoset, either one or two part, or a thermoplastic. For example, a bundle of continuous glass fibers may be impregnated with a thermosetting resin and then pulled through a heated pultrusion die to cure the resin and make composite parts such as ladder rails. Fibers have been treated in other off-line processes such as filament winding by feeding the fibers through a bath of curable resin and then winding and curing the fibers to form filament wound parts.
However, in such off-line processes, the continuous glass fibers must be separated in some manner to allow impregnation of the resin between the fibers and then recombined. This almost always involves the use of additional hardware such as spreader bars, impregnation baths, and drying or curing ovens. These types of processes have the disadvantage that they add cost and complexity to the process. In addition, the resultant extra handling of the glass fibers can cause breakage of the individual glass filaments and, thereby, a degradation of the properties of the composite article. Therefore, while such off-line processes may be effective, they are time consuming and inefficient (i.e., always requiring additional process steps) and, thus, expensive. Accordingly, there is a need in the art for an efficient and cost effective in-line process for applying a chemical treatment to glass and other fibers so as to form a pre-impregnated ("prepreg") glass/polymer composite bundle or strand, where the resulting prepreg strand is suitable for subsequent processing into a composite article with little or no additional resin treatment.